Single shot fast spin echo diffusion-weighted MR imaging of the spine; Is it useful in differentiating malignant metastatic tumor infiltration from benign fracture edema?

PURPOSE

This study aims to evaluate the usefulness of single shot fast spin echo diffusion-weighted MR imaging (DWSSFSE) in differentiating malignant metastatic tumor infiltration of vertebral bone marrow from benign vertebral fracture edema.

MATERIALS AND METHODS

Forty-six consecutive patients with 59 acute osteoporotic or traumatic vertebral fractures (mean age = 59) and 31 patients with 98 vertebral metastasis including 20 pathologic fractures (mean age = 53) were included in this study. Diffusion-weighted MR images were obtained by single-shot fast spin echo technique with diffusion gradient (b = 500 s/mm2, TR/TE: 5002/99) by using a 1.5 T MR scanner (Signa MR/i; GE Medical Systems, Milwaukee, WI, USA). T1- and T2-weighted images and short inversion time inversion-recovery (STIR) images were available in all 157 lesions, while contrast-enhanced images were available in 98 metastatic lesions. We evaluated signal intensity patterns on DWSSFSE in 157 lesions, which showed low signal intensity on T1-weighted images in both benign fractures and metastasis. The lesions on DWSSFSE were categorized as low, intermediate, and high signal intensity relative to presumed normal vertebra by concordant inspection of two experienced musculoskeletal radiologists.

RESULTS

In benign fractures, DWSSFSE images showed low signal intensity in 56 vertebrae (95%) in 43 patients (93%) and intermediate signal intensity in only 3 vertebrae (5%) in 3 patients (7%). On the other hand, metastases most commonly had low signal intensity in 57 vertebrae (58%) in 25 patients (80%), intermediate signal intensity in 35 vertebrae (36%) in 16 patients (52%), and high signal intensity in 6 vertebrae (6%) in 3 patients (10%). Thus, intermediate and high signal intensities are far more common than benign fractures. Such differences in signal intensity were statistically significant (chi-square test, P < .05). High or intermediate signal intensity on DWSSFSE was highly specific for the diagnosis of metastatic tumor infiltration of the spine (sensitivity: 42%; specificity: 95%; true positive rate: 93%; false negative rate: 52%).

CONCLUSIONS

DWSSFSE of the spine may be useful in differentiating metastatic tumor infiltration of vertebral bone marrow from benign fracture edema.